The present invention relates generally to the data processing field, and more particularly, relates to a method and apparatus for detection of the presence of slider airbearing resonance using surface analysis test (SAT) P-list data.
Techniques for detecting disk surface defects are known. Most commercially available disk drives store a standard primary defect list (P-list) and a grown defect list (G-list) in a protected area of the disk drive, often referred to as disk defect logs. The P-list is generated for each disk file at manufacturing time and stores information of specific locations of magnetic surface defect sites and the alternate site for storing data. The G-list is generated and periodically updated while the disk drive is in use including stored information of grown defects that occurred after manufacturing.
Special manufacturing slider-glide-test procedures, such as Harmonic Ratio Flyheight (HRF) and Clearance Modulation Detection (CMD) typically are used to detect the presence of airbearing resonances in direct access storage device (DASD) sliders.
It is desirable to provide a method and apparatus for detection of slider airbearing resonance that eliminates the need for Special manufacturing slider-glide-test procedures, such as Harmonic Ratio Flyheight (HRF) and Clearance Modulation Detection (CMD). A need exists for an improved method and apparatus for detection of slider airbearing resonance.
A principal object of the present invention is to provide an improved method and apparatus for detection of the presence of slider airbearing resonance. Other important objects of the present invention are to provide such method and apparatus for detection of the presence of slider airbearing resonance substantially without negative effect and that overcome many of the disadvantages of prior art arrangements.
In brief, a method and apparatus are provided for detection of the presence of slider airbearing resonance using surface analysis test (SAT) P-list data. The P-list in the disk drive is selected. Checking for a cluster threshold of adjacent tracks within a sector to identify a SAT cluster is performed. Responsive to identifying the SAT cluster, checking for multiple defects on some tracks within the SAT cluster is performed. Responsive to identifying multiple defects on some tracks within the SAT cluster, the SAT cluster is converted to a binary matrix map. A histogram is generated for the binary matrix map. The harmonic magnitude content of the histogram from harmonics centered about a slider airbearing resonance frequency fa is identified.
In accordance with features of the invention, a harmonic power ratio (HPR) for the SAT cluster is computed and compared with a harmonic power ratio threshold. Responsive to the computed HPT being greater than the harmonic power ratio threshold, a wave-front frequency of the SAT cluster is computed. The wave-front frequency fw of said SAT cluster is represented by:                               fa          ~          fw                =                                            ∑                              k                =                                  k                  1                                                            k                2                                      ⁢                          xe2x80x83                        ⁢                                          A                ⁡                                  (                  k                  )                                            ⁢                              f                ⁡                                  (                  k                  )                                                                                        ∑                              k                =                                  k                  1                                                            k                2                                      ⁢                          xe2x80x83                        ⁢                          A              ⁡                              (                k                )                                                                        Equation        ⁢                  xe2x80x83                ⁢        1            
where A(k) is the harmonic magnitude of the DFT at harmonic frequency f(k) and k is the harmonic frequency index and k1 and k2 are computed harmonic indices.